Multi-RAT Network (or System)
Multi radio access technology (multi-RAT) network is a wireless communication environment in which there exist two or more heterogeneous networks, and a terminal can access two or more heterogeneous networks to simultaneously perform communication.
Heterogeneous network (or heterogeneous system) refers to a network using a communication scheme which is different from that of a specific network on the basis of the specific network. For example, a WiMAX network which is an example of a mobile communication system and a Wi-Fi network which is an example of WLAN may be heterogeneous networks with respect to each other.
Further, RAT is a technology type used in radio access. For example, RAT may include GSM/EDGE Radio Access Network (GERAN), UMTS Terrestrial Radio Access Network (UTRAN), Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN), WiMAX, LTE(-A), WiFi, and the like. In other words, GERAN, UTRAN, E-UTRAN, WiMAX and/or WiFi may be intermixed in the same area.
In addition, a terminal capable of accessing two or more heterogeneous networks to perform communication, i.e., capable of supporting multi-RAT, may be referred to as a “multi-system terminal” or “multi-mode terminal.”
In recent years, terminals supporting both a cellular network and WLAN have been typically on the market in a broadband wireless communication system. Each system has different characteristics (advantages or disadvantages), and thus may perform a complementary operation, thereby providing enhanced services. The following Table 1 illustrates the characteristics of a cellular network and WLAN.
Table 1
TABLE 1ProsConsNoteWLANHigher BW- LowUncontrolled Mobility- NoWLAN provides -cost for deployment-connection management-Higher BW/LowLow overhead forLimited QoS support- HighlatencyCellularmaintaining connections- power consumption for networkprovides - QoSLow accessdiscovery - Hard to managing interference- support- Mobility/delay for randomSevere performanceconnectionaccess with smalldegradation with the largemanagement- Coordinatesnumber of MSsnumber of MSstheCellularMobilityHigher access delay fordevices to connectManagement-scheduled access- Large controlWLANGuaranteed QoSoverhead for data transmissionsupport Securetransmission
A multi-RAT terminal may typically perform communication via a cellular network, but may also transmit and receive data by using WLAN AP when the WLAN AP is located in the vicinity. Even in this case, when WLAN cannot support QoS in case of a service in which the QoS should be guaranteed such as a phone service, the multi-RAT terminal may transmit data via a cellular network. In other words, a multi-RAT terminal can perform data communication using a more excellent network, and in the aspect of a system, high-speed data transmission is dispersed into WLAN, thereby increasing an overall system efficiency.
However, even if the terminal has a capability for accessing multi-radio access technology (multi-RAT) in a wireless communication environment supporting two or more heterogeneous networks in the related art, it may be impossible to simultaneously transmit and receive data via two or more heterogeneous networks by simultaneously accessing multi-radio access technology. In other words, in case of a terminal supporting multi-radio access technology in the related art, any one wireless access technology is accessed based on a switching mechanism to transmit or receive data via one network. Accordingly, when a terminal having multi-RAT capability transmits and receives data via a specific network and then via a network which is different from the specific network, data transmission and reception via either one network should be terminated.
In other words, according to the related art, a terminal having capability supporting two or more heterogeneous networks can perform communication using different networks, but operates based on a simple switching mechanism, thereby having a limit in the efficiency. For example, since different networks are operated in an independent manner, the management may be inefficiently carried out in the aspect of security/authentication, IP flow mobility, network discovery, and the like.